Continuous spinal anesthesia procedures and continuous epidural anesthesia procedures are of course well known in the art. In either case, the distal end of the catheter is first introduced into the patients body with the proximal or trailing end outside the body to receive the anesthetic.
To do so, an adapter is employed connecting the proximal end of the catheter at one end of the adapter to a source of liquid anesthetic, e.g. a syringe, at the other. The adapter has a channel communicating with the catheter end so that when the liquid anesthetic is introduced into the channel, it passes through the catheter into either the subarachnoid space, if the spinal anesthesia procedure is used or into the epidural space, as would be the case with the epidural anesthesia procedure.
As an illustration of prior adapters for this purpose, mention may be made of those described and claimed in U.S. Pat. No. 4,187,848 issued to Glenn N. Taylor. As disclosed therein, the adapter comprises two separate members, one being designated as the body member, the other being termed a compression member. The body member has an elongated bore and an opening at its distal end for receiving the proximal end of the catheter extending from the patient's body. An elongated elastic plug having a channel extending therethrough is seated in uncompressed condition within the bore of the body member, the channel being aligned with the opening of the body member so that the catheter end inserted in the opening can be positioned within the plug channel. The compression member has a port at its proximal end where the tip of a syringe may be releasable engaged for injecting liquid anesthetic. A passageway for fluid extends between the two ends of the compression member so that when the proximal end of the body member and the distal end of the compression member are secured together, the liquid anesthetic injected from the syringe may be pumped into the catheter. To connect the two members, the proximal end of the body member is provided with external threads and the distal end of the compression member with internal threads mating with the body member threads. When the threads are tightened to secure the two members, the plug is compressed to retain the catheter end positioned therein.
The aforementioned parent application, Ser. No. 400,859, relates to an improved adapter wherein the catheter connector and syringe connector are movably pre-connected with respect to each other from an open position to insert the catheter end and a closed position to secure the catheter in place. Anti-back-off means are provided to retain the connector in the closed position, thereby locking the catheter end in the adapter until released by disengaging the anti-back-off means. In the preferred embodiment, means are also provided for preventing overtightening of the connector, which overtightening will cause excessive compressive force to be exerted on the catheter, causing unwanted lowering of its gap through which the anesthetic must traverse as well as possible damage to the catheter.
In both the adapters of the prior art, as exemplified by the aforementioned U.S. Pat. No. 4,187,848, and the improved newer version described and claimed in the parent application, Ser. No. 400,859, there is an inherent problem of kinking of the catheter at a point just external of where the proximal end of the catheter is engaged within the distal opening of the adapter. This kinking, caused by acute bending of the catheter, can materially diminish if not totally inhibit the flow of liquid anesthetic through the catheter.
It is to this kinking problem to which the present invention is directed.